[Pre-pathologic-pathologic cardiotocographic pattern in second stage of labor. Analysis of the incidence of acidosis and recommendations for fetal blood gas analysis].

Fetal heart rate (FHR) patterns from 746 consecutive, documented vaginal deliveries within a 1 year period were reported on using the Hammacher Score. Characteristic FHR patterns were described and the frequency of acidosis calculated. FHR score, the single FHR parameters, baseline (BL), floatingline (FL) and oscillation type (OT) and the acid-base balance of the neonate were submitted to a correlation analysis according to Spearman. FHR patterns reported as ominous (FHR score > or = 5) were observed in 25.9% and were associated with a frequency of acidosis (pHUA < or = 7.20) of 38.1% Suspicious fetal heart rate patterns (FHR score 3-4) were seen in 60%, here the frequency of acidosis was 8.5%. With the inclusion of decelerations by the parameter FL an increased frequency of acidosis of 29% was registered only when 4 points were allocated. Total FHR score and the score parameter baseline (BL) correlated closest with the pH changes at the end of birth. Tachycardic FHR patterns showed the highest frequency of acidosis (55%) and ominous tracings (83%). The commonest FHR pattern, normocardia with decelerations (48%) exhibited only a low frequency of acidosis (8%) and ominous tracings (15%) with an average pH value of 7.27 +/- 0.08. To prevent an unnecessary operative delivery in the presence of an ominous FHR finding, whether in the late first stage or early second stage when birth is not imminent, a fetal blood analysis should be carried out. With a suspiciously assessed fetal heart rate pattern the fetal blood analysis will only rarely reveal a severe acidosis (pHUA < or = 7.10).